This invention relates to the general field of centrifugal blowers, such as those used for automotive climate control.
Centrifugal impellers generally include multiple blades that turn incoming airflow toward the radial direction as it moves from the impeller inlet to the impeller outlet. The blades generally are attached to, and rotate with, a hub, which defines the airflow path on the base of the impeller (the side opposite the inlet). For two-piece impellers, the top of the airflow path is established by a top shroud, which also is attached to the blades and rotates with the blades and the hub.
In automotive climate control applications (i.e., heating, ventilation and air conditioning) centrifugal impellers generally can be placed into two categories: a) low cost, single-piece impellers; and b) higher cost, higher efficiency two-piece impellers. The single-piece impellers, because of their lower cost, generally are used much more often than two-piece impellers. Two-piece impellers generally are used where the need for high efficiency or high pressure capability outweighs the cost disadvantage.
In automotive climate control applications, centrifugal blowers should operate efficiently over a range of operating conditions. For example, duct passages open and close to direct air through different heat exchangers of different flow resistances. Flow resistance typically is greatest in heater and defrost conditions, and least in air conditioning mode. In some instances, the high flow resistance of heater and defrost modes can cause performance and noise problems for conventional one-piece impellers that may be less efficient or only capable of producing relatively low pressures.
Yapp, U.S. Pat. No. 4,900,228 discloses a two-piece impeller with rearwardly curved blades with xe2x80x9cSxe2x80x9d shaped camber.
Chapman (WO 01/05652) discloses a two-piece impeller with high blade camber.
This invention provides blade and passage geometry found in two-piece centrifugal impellers in a design that can be injection molded as a single piece. The injection mold does not require any action or slides to mold the part.
In general, the invention features a centrifugal impeller constructed as a single part. The impeller includes three components: i) a plurality of blades, each having a leading edge and a trailing edge; ii) a generally annular top shroud connected to the tops of the blades, the top shroud having an inner radius; and iii) a hub connected to an inner portion of the base of the blades, the hub having an outer radius that is less than the inner radius of the top shroud, so that the blades, top shroud and hub can be constructed as a single unit. The invention is less expensive to manufacture than a two-piece impeller and operates more efficiently and at higher flow resistances than a conventional one piece impeller.
Another aspect of the invention is a blower assembly comprising the above described impeller and a base-plate, which, together, form an airflow path from an inlet to an outlet. The base-plate is non-rotating and extends outwardly to a radius greater than the impeller hub radius. The clearance between the base plate and the impeller blades is generally less than 10 percent of the radius of the bottoms of the blade trailing edges. In preferred embodiments, the base plate is curved in a plane which contains the impeller axis, and is contoured to match the contour of the base of the impeller blades as the impeller rotates.
In some preferred embodiments, the impeller is contained in a blower housing and said base plate is integrated into a portion of said blower housing as a single monolithic part. In some preferred embodiments, a motor is mounted to rotate the impeller, said motor being mounted to a motor flange, and said base plate is integrated into said motor flange as a single monolithic part. In some preferred embodiments, a motor is mounted to rotate the impeller, said motor being mounted in a motor housing, and said base plate is integrated into said motor housing as a single monolithic part. In some preferred embodiments, said motor housing is integrated into a portion of the blower housing as a single monolithic part.
In preferred embodiments, the blower assembly is sized and configured to be installed in an automotive climate control system.
In preferred embodiments, the impeller is characterized by:
a) a top shroud that has curvature in a plane that contains the impeller axis;
b) a cylindrical area ratio between 1.0 and 2.0;
c) an inlet to outlet area ratio between 0.7 and 1.0;
d) blades that make contact with the hub over less than 20% of the blade meanline length at the base of the blade;
e) a minimum blade chord length of 15% of the impeller diameter;
f) a blade solidity of at least 2.0;
g) tops of the blade leading edges that protrude radially inward to a radius 1-8 millimeters less than the impeller inlet radius;
h) a top shroud that covers the blades over at least 50% of the radial extent of the blades that is greater than the impeller inlet radius, and;
i) a top shroud that incorporates a ring that is used to control the recirculation through the clearance between the impeller and the blower housing.
The invention features a method of injection-molding the above-described impeller as a single piece. It also features a method of assembling a blower assembly in which a motor is attached to a motor housing, a motor flange, or a portion of a blower housing in which a base plate has been integrated, and the above-described impeller is attached to the motor in such a way as to control the clearance between the impeller and the base plate.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.